1. Field of the Invention
The invention relates to refractive-index sensors and, particularly, to a refractive-index sensor based on photonic crystals.
2. Description of Related Art
Recently, there has been interest in using photonic crystals to measure refractive index change for sensing applications, because of the unique light-confinement mechanism provided by the photonic bandgap. Photonic crystals provide the potential for a high quality factor (high-Q) microcavity and a small sensing area. For example, the sensing area may be 10□ μm2, which requires only a very small amount (e.g., 10−15 liters) of sample. These advantages make the photonic crystal an attractive candidate for use in measuring small samples. Thus, the refractive-index sensor based on photonic crystals has been developed extensively.
A conventional refractive-index sensor based on photonic crystals that is capable of detecting a change in refractive index of 0.2 has been proposed. However, the resolution of the refractive-index sensor is limited. In addition, another conventional refractive-index sensor with a two-dimensional photonic crystal microcavity has been proposed. The refractive-index sensor can measure a sample having a refractive index (n) within a range from n=1.0 to n=1.5. However, the refractive-index sensor has low light transmission. The refractive-index sensor also has drawbacks such as low sensitivity and low accuracy of measurement.
What is needed, therefore, is a refractive-index sensor having high light transmission and improved accuracy of measurement as well as improved sensitivity.